Polyacrylate elastomers are well-known and widely used in applications where low temperature flexibility and resistance to hydrocarbon oils is important, e.g., in automotive applications; see Kaizerman, U.S. Pat. No. 3,201,373; and Vial, Rubber Chem. and Tech. 44, 344-362 (1971).
Particularly useful polyacrylate elastomers are those comprising a major proportion of one or more alkyl acrylates wherein the alkyl group contains 2-8 carbon atoms copolymerized with a minor proportion of an active-halogen containing ethylenically unsaturated co-monomer, such as vinyl chloroacetate, vinyl chloroethyl ether, 2-chloroethyl acrylate, and the like. Copolymers of ethyl acrylate and vinyl chloroacetate provide outstanding resistance to swelling in contact with hydrocarbon oils, but only a moderately low glass transition temperature (.about.-18.degree. C.). Copolymers of butyl acrylate and vinyl chloroacetate, on the other hand, have outstanding low temperature properties (Tg.about.-44.degree. C.) but relatively poor resistance to hydrocarbon oils. Combinations of ethyl acrylate and butyl acrylate provide elastomers having intermediate properties. Other means have been suggested for improving the hydrocarbon oil resistance of butyl acrylate copolymers, such as copolymerization with 2-cyanoethyl acrylate (see Aloia, U.S. Pat. No. 3,397,193); or providing copolymers of combinations of monomers, such as alkoxyalkyl acrylates and alkylthioalkyl acrylates. Invariably, improvement in one of the properties is achieved at the sacrifice of the other.